INTRODUCTION
SNMP is an Internet standard protocol to manage devices on IP networks. More precisely, its the standard way of monitoring hardware and software from any manufacturer from Cisco to Juniper and from Microsoft to Linux. SNMP uses UDP as the transport protocol and usually works on 161 port no.
There are three versions of SNMP:
SNMPv1 (Initial implementation of SNMP Protocol)
SNMPv2 (Improvement in performance)
SNMPv3 (Adds security and remote configuration enhancement)
SNMP Terminologys
1) OID (Object Identifier)
OID is something that gathers information about. On SNMP enabled device.
Its identified by name object name. It can access range of information.
eg. CPU- Speed/Utilization
Memory- Total/ Used/ Free
Interface up down status
2) MIB ( Management information base )
MIB's are collection of OID's
SNMP agent retrieves value of the requested info from the MIB when the SNMP manager request.
MIB files are set of question that a SNMP manager can ask the agents
SNMP Components
1) SNMP Manager
2) SNMP Agent
3) Managed Device
1) SNMP Manager:
SNMP manager role is to collect information from SNMP agent of SNMP manager device and displays information in readable form. eg. Solarwinds.
2) SNMP Agents:
Every manufacturer configures SNMP agent on the managed device. Collects management information on the managed device. Agent collects management info about its local environment. Stores and retrieves information as store in the MIB. Signal an event to the manager.
eg. Windows- SNMP, Linux net-SNMP, Cisco- cisco-SNMP.
3) Managed Device:
Managed device could be any network device (such as switch or router) or could be any server ( physical or virtual) with any os. In simple way it could be any device with an IP and a SNMP agent.
Standard Flow
SNMP Manager ====> SNMP Agent ====> Managed Devices
There are five primary types of SNMP messages – TRAP, GET, GET-NEXT, GET-RESPONSE, and SET used as means of communication between the SNMP agent and the SNMP manager.
SNMP Traps
The most frequently used SNMP messages are traps. These are sent to the manager by an agent when an issue needs to be reported. SNMP traps are quite unique if compared to other message types, since they are the only method that can be directly initiated by an SNMP agent.SNMP trap is a widely used mechanism to alert and monitor a devices’ activities across a network.
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